Field
Embodiments of the present invention generally relate to an apparatus and method for depositing or removing materials on a substrate. More particularly, embodiments of the present invention relate to an apparatus and method for controlling the intensity and/or distribution of a plasma discharge in a plasma chamber.
Description of the Related Art
Plasma enhanced processes, such as plasma enhanced chemical vapor deposition (PECVD) processes, high density plasma chemical vapor deposition (HDPCVD) processes, plasma immersion ion implantation processes, and plasma etch processes, have become common processes used in depositing materials on substrates and/or removing materials from a substrate to form structures.
Plasma provides many advantages in manufacturing semiconductor devices. For example, using plasma enables a wide range of applications due to lowered processing temperature, enhanced gap-fill for high aspect ratio gaps, and higher deposition rates.
A challenge that is present in conventional plasma processing systems is the control of the plasma to attain uniform etching and deposition. A key factor in the etch rate and deposition uniformity is the spatial distribution of the plasma during processing. For example, in a conventional PECVD chamber, which are typically parallel plate reactors, the traditional factors affecting the spatial distribution of the plasma are chamber pressure, distance between electrodes, and chemistry, among other factors. While conventional control of plasma distribution in PECVD chambers produces satisfactory results, the process may be improved. One challenge that remains in plasma processing is non-uniformity or uneven deposition of bulk material, such as conductive materials, dielectric materials, or semiconductive materials, to form a thin film on the substrate.
FIG. 1A (prior art) is a cross-sectional view of a substrate 1 illustrating one challenge caused, at least in part, by non-uniformity in conventional plasma chambers. The substrate 1 includes a plurality of structures 5, which may be trenches, vias, and the like, formed therein. A layer 10 of conductive, dielectric, or semiconductive material formed thereon by a conventional plasma process substantially covers the substrate 1 and fills the structures 5. The substrate 1 has a dimension D1, which may be a length or width in the case of a rectangular substrate, or an outside diameter in the case of a round substrate. In this example, substrate 1 is a round substrate and dimension D1 is an outside diameter, which may be equal to about 300 mm or 200 mm.
As stated above, the layer 10 substantially covers the substrate 1 but effectively stops at a dimension D2, which leaves a peripheral portion of the substrate 1 having little or no material thereon. In one example, if dimension D1 is 300 mm, dimension D2 may be about 298 mm, which produces about a 1 mm portion around the periphery of the substrate 1 having little or no material thereon, which reduces device yield on the substrate 1 as the periphery of the substrate 1 is effectively unusable. Such defects are sometimes referred to as edge effects or plasma edge effects.
FIG. 1B (prior art) is an exploded cross-sectional view of substrate 1 of FIG. 1A showing a surface area 20 on the periphery of the substrate 1 illustrating another challenge caused, at least in part, by non-uniformity in conventional plasma chambers. The edge region 25 is shown uncovered due to the device yield reduction described above. In addition, conventional plasma processes may produce region 15 along the periphery of the substrate, which may be an area where excessive deposition and build-up of material occurs. In subsequent processes, substrate 1 may undergo a chemical mechanical polishing (CMP) process or other planarization or polishing process to remove a portion of layer 10. In the subsequent process, region 15 may create challenges since region 15 must be removed along with layer 10. As region 15 may include a height D3 of between a few hundred angstroms (Å) to thousands of Å above surface area 20 of layer 10, throughput may be negatively impacted in the subsequent process. Additionally, removal of region 15 may cause overpolishing of surface area 20, which may result in damage to devices or structures formed on substrate 1.
Therefore, there is a need for an apparatus and method to provide enhanced control of the spatial distribution of plasma in a plasma chamber to address the challenges described above.